Old, Fat Mice Blamed for Virus Transmission

WEDNESDAY, Jan. 7 (HealthDay News) -- Stemming an often fatal virus linked to deer mice might mean focusing on the older and bigger mice. They're the ones most likely to spread the disease, researchers from the University of Utah have found.

Known as the Sin Nombre virus, the hantavirus -- meaning a virus spread by contact with rodent urine and feces -- causes a lung disease in people that has proven fatal about 35 percent of the time, according to data from the U.S. Centers for Disease Control and Prevention. The disease, named hantavirus pulmonary syndrome, has been reported in 30 states, including most of the western half of the United States.

It's usually spread from deer mice to people when droppings are inhaled. But what the researchers discovered was how the hantavirus is most often spread from mouse to mouse.

With the aid of fluorescent talcum powders and implanted radio transmitters, the researchers tracked the comings and goings of deer mice at 12 sites on federal land in the western Utah desert over two 15-day periods.

The number of contacts that a mouse had with other mice did not affect its likelihood of having the virus. Nor did the length of those contacts. But when the researchers combined the data, they found a connection. Mice with either a few long contacts or many short ones were more apt to have the hantavirus.

They also found that the mice with the most contacts were about 11 percent heavier than the other mice.

"The biggest individuals are most likely to be the ones with the largest foraging range, because they have to get more food," researcher Christy Clay said in a statement released by the university. "Or, they could be territorial, so they are defending a nest or their food resource."

And, Clay said, "if they are bigger, they are older."

The findings were published online Jan. 7 in the British biological research journal Proceedings of the Royal Society B.

Knowing where deer mouse populations thrive -- where mice grow older and bigger thanks to ample food, protection and nesting sites -- should help people avoid contact with the creatures or their droppings, the researchers suggested.